@article {48670, title = {High open-circuit voltage in lead sulfide quantum dot solar cells via solution-phase ligand exchange with low electron affinity cadmium halides}, journal = {JOURNAL OF MATERIALS CHEMISTRY A}, volume = {11}, year = {2023}, month = {AUG}, pages = {17282-17291}, type = {Article}, abstract = {

The deployment of colloidal quantum dots (QDs) in building high-performance solar cells and other optoelectronic applications relies on the passivation of unsaturated surface atoms through ligand engineering to attain a trap-free energy bandgap and strong QD coupling while maintaining the quantum confinement effect. Despite major advancements in surface passivation strategies, the open circuit voltage (V-oc) of lead sulfide (PbS) QD solar cells is limited by undesirable sub-bandgap states and high-bandtail states. The most advanced solution-phase ligand exchange strategy for PbS QDs depends on lead halide ligands, which improved the photocurrent and fill factor in QD solar cells significantly, but only an incremental change in V-oc is observed. Here we showcase a solution-phase hybrid ligand passivation strategy for PbS QDs using shallow electron affinity cadmium halide and thiol ligands. The cadmium halide ligand treatment results in the sub-monolayer substitution of surface Pb atoms by Cd atoms. The photophysical properties of QDs improve significantly to show intense band edge emission, diminished trap emission and reduced Urbach tail states. The photovoltaic devices built using cadmium halide-treated QDs show low reverse saturation current, which helps to attain a record 0.7 V V-oc (for a 1.28 eV bandgap) and 12.3\% PCE.

}, issn = {2050-7488}, doi = {10.1039/d3ta02191b}, author = {Dambhare, Neha V. and Biswas, Arindam and Sharma, Anjali and Shinde, Dipak Dattatray and Mahajan, Chandan and Mitra, Anurag and Rath, Arup K.} } @article {49241, title = {Solution-phase ligand engineering for all-quantum-dot near-infrared light-emitting diodes}, journal = {ACS Applied Nano Materials}, volume = {7}, year = {2024}, month = {APR }, pages = {9126-9135}, type = {Article}, abstract = {

Strong emission over a wide near-infrared (NIR) region makes lead sulfide quantum dots (QDs) a preferred material in building NIR light-emitting diodes (NIR-LEDs) for numerous applications. Narrow-bandgap emitter QDs blended in the matrix of high-band gap QDs offer a simple yet powerful architectural platform for building high-performance NIR-LEDs. So far, the all-QD-based blend architecture has been realized using a poorly controlled solid-state ligand exchange approach. Advanced solution-phase ligand exchange, which offers greater control over surface passivation, is yet to be realized in all-QD LED device construction. We observe that the solution-phase ligand exchange from the optimized lead halide and thiol ligand combination, used in high-performing QD solar cell construction, is inefficient in realizing efficient all-QD LEDs, which could have restricted the adoption of the solution-phase ligand exchange thus far. Here, we introduce an innovative dual-ligand strategy to build all-QD-based NIR-LEDs using an advanced solution-phase ligand exchange approach. Through ligand engineering of matrix QDs, we managed to improve photoluminescence quantum yield (40\%), reduce trap density (10(14) cm(-3)), and prolong carrier lifetime (832 ns). The LED devices benefit from improved electronic properties and balanced carrier injection to yield 6\% EQE and 7.7\% PCE, which are six times higher than those of state-of-the-art ligands.

}, keywords = {electroluminescence, lead sulfide, ligand passivation, light-emitting diodes, near-infrared, quantumdots}, doi = {10.1021/acsanm.4c00634}, author = {Biswas, Arindam and Mitra, Anurag and Sharma, Ashish and Shinde, Dipak Dattatray and Dambhare, V. Neha and Sharma, Anjali and Mahajan, Chandan and Rath, Arup K.} } @article {49328, title = {Synthesis and processing strategy for high-bandgap PbS quantum dots: a promising candidate for harvesting high-energy photons in solar cells}, journal = {ACS Applied Materials \& Interfaces}, volume = {16}, year = {2024}, month = {AUG }, pages = {42522-42533}, type = {Article}, abstract = {

The wide tunability of the energy bandgap of colloidal lead sulfide (PbS) quantum dots (QDs) has uniquely positioned them for the development of single junction and tandem solar cells. While there have been substantial advancements in moderate and narrow bandgap PbS QDs-ideal for single junction solar cells and the bottom cell in tandem solar cells, respectively; progress has been limited in high-bandgap PbS QDs that are ideally suited for the formation of the top cell in tandem solar cells. The development of appropriate high bandgap PbS QDs would be a major advancement toward realizing efficient all-QD tandem solar cells utilizing different sizes of PbS QDs. Here, we report a comprehensive approach encompassing synthetic strategy, ligand engineering, and hole transport layer (HTL) modification to implement high-bandgap PbS QDs into solar cell devices. We achieved a greater degree of size homogeneity in high-bandgap PbS QDs through the use of a growth retarding agent and a partial passivation strategy. By adjusting the ligand polarity, we successfully grow HTL over the QD film to fabricate solar cells. With the aid of an interface modifying layer, we incorporated an organic HTL for the realization of high-performance solar cells. These solar cells exhibited an impressive open-circuit voltage of 0.824 V and a power conversion efficiency of 10.7\%, marking a 360\% improvement over previous results.

}, keywords = {charge transport, lead sulfide, ligand passivation, quantum dots, solar cell}, issn = {1944-8244}, doi = {10.1021/acsami.4c09364}, author = {Shinde, Dipak Dattatray and Sharma, Anjali and Dambhare, Neha V. and Mahajan, Chandan and Biswas, Arindam and Mitra, Anurag and Rath, Arup K.} }